Samaniite
Chemical formula: Cu<sup>1+</sup><sub>2</sub>Fe<sup>2+</sup><sub>5</sub>Ni<sup>2+</sup><sub>2</sub>S<sup>2-</sup><sub>8</sub>
Samaniite is an extremely rare copper, iron, and nickel sulfide, forming microscopic, metallic grains in ultramafic volcanic rocks.
Properties
- Mohs hardness
- 4
- Luster
- Metallic
- Streak
- Black
- Density
- 4.85
- Cleavage
- None
- Fracture
- Uneven
- Transparency
- Opaque
- Crystal system
- Tetragonal
Diagnostic features
## Identification Identification of samaniite is possible only using advanced laboratory techniques. In reflected light under a polarizing microscope, it has a grayish color with a yellowish tint and is weakly anisotropic. Final confirmation requires chemical analysis (e.g., using an electron microprobe) to determine the composition (presence of Cu, Fe, Ni, and S in appropriate proportions) and X-ray diffraction to confirm the crystal structure. ## Distinguishing from similar minerals Samaniite occurs in paragenesis with other sulfides, such as pyrrhotite, pentlandite, and chalcopyrite. It is distinguished from chalcopyrite by its less intense yellow color. From pentlandite, with which it forms intergrowths, it is difficult to distinguish visually and requires chemical analysis. Compared to pyrrhotite, samaniite is slightly brighter. ## Crystal forms This mineral forms exclusively anhedral, irregular grains, often with rounded contours. It typically occurs as fine inclusions in pyrrhotite or at the grain boundaries of pyrrhotite and pentlandite. It has not been observed in the form of well-developed crystals.
Geological environment
## Genesis Samaniite is a mineral of magmatic origin. It forms in ultramafic volcanic rocks, specifically dacites, which are part of ophiolite complexes. It crystallizes from a residual, sulfide-rich magmatic liquid in the late stage of its solidification, under relatively low temperatures (below 400°C). ## Mineral associations This mineral occurs in close association with other sulfides. It is most often accompanied by pyrrhotite (both hexagonal and monoclinic), pentlandite, and chalcopyrite. It also co-occurs with magnetite. ## Localities The only confirmed occurrence of samaniite in the world is its type locality: the Horoman ophiolite complex, located in the Samani massif, within Samani town, Hidaka Subprefecture, on Hokkaido Island, Japan.
Rarity
Extremely rare
For collectors
## Quality criteria Samaniite is a mineral of purely scientific significance and does not appear on the collector's market as a standalone specimen. Its value lies in its presence in research samples from the type locality. Since it is a microscopic mineral, typical evaluation criteria such as size, color, or purity do not apply to it. The attractiveness of a specimen containing samaniite is identical to the quality and richness of the sulfide paragenesis in a given rock sample. ## Popular localities The only source of material in which samaniite has been identified is the Samani massif in Japan. Specimens from this locality, containing confirmed samaniite, are extremely rare and are mainly found in the collections of scientific institutions.
Care and storage
## Cleaning Due to its microscopic nature and occurrence as inclusions in other minerals, isolated cleaning of samaniite is not practiced. Specimens containing samaniite should be treated according to the requirements of the dominant mineral (matrix), most often pyrrhotite. Usually, a gentle wipe with a dry, soft cloth or brush is sufficient to remove dust. ## What to avoid Avoid contact with chemicals, acids, and strong detergents, which can react with sulfides and damage both samaniite and the surrounding minerals. Pyrrhotite, in which samaniite often occurs, is sensitive to moisture and can oxidize, so storage in humid conditions should be avoided. ## Storage Specimens should be stored in a dry, stable environment, preferably in closed collector boxes or display cases, to protect them from dust and changes in humidity. Avoid direct exposure to sunlight and extreme temperature changes.